“We have a great opportunity ahead of us,” D.C. United Coach Ben Olsen said. “For me, it’s exciting. The guys are excited too. We know what we have to do: We have to start winning games.” (Jonathan Newton/The Washington Post)

D.C. United is probably going to need to win three of its final four matches to claim an MLS playoff berth. Given the schedule — Wednesday’s game against the league’s worst club followed by three home events — it’s a reasonable expectation.

But at some point during this 11-day stretch, United will have to win consecutive matches — something it has failed to do in league play since June 2009. The group will also need to secure most, if not all, of the potential points at RFK Stadium, where, inexplicably, United hasn’t fared as well as on the road.

“We have a great opportunity ahead of us,” Coach Ben Olsen said. “For me, it’s exciting. The guys are excited too. We know what we have to do: We have to start winning games.”

United (9-10-11, 38 points) will start the final leg Wednesday night in Vancouver, B.C., against the expansion Whitecaps (5-16-10, 25), then return home to face the playoff-contending Chicago Fire, Portland Timbers and Sporting Kansas City over eight days.

At the moment, United is not in the 10-team MLS postseason field — six points from an automatic berth in the Eastern Conference and five from a wild-card slot. But having played two fewer matches than most of its competitors, United is positioned to make a substantial move over the next week and enter the final weekend without needing to rely on other results.

Failure to qualify for the playoffs would stretch D.C.’s drought to four seasons — the longest in club history.

“We’re not in panic mode, but there is a sense it’s time to grab some points,” captain Josh Wolff said. “We can’t look to other teams; we’ve got to do it on our own.”

Winning at Vancouver is not as simple as it seems. Despite a poor overall record, the Whitecaps are a respectable 5-5-5 at home and eager to avenge a 4-0 loss in Washington in August, a result that matched their worst defeat of the year. They are coming off of a 3-0 victory over playoff-bound Real Salt Lake last week.

United has lost three straight away games after a 4-1-4 run on the road and will probably be without its most influential player, Dwayne De Rosario, who was with Canada’s national team for a 2014 World Cup qualifier Tuesday night in Toronto.

Early Tuesday, Olsen wasn’t ruling out the possibility of De Rosario making a trans-continental trip; it depended largely on playing time against Puerto Rico, Olsen added. (De Rosario played all 90 minutes in the 0-0 draw).

United, however, is probably more inclined to rest De Rosario, 33, ahead of the hectic home stretch. Traveling 2,080 miles to play on consecutive days, then flying 2,340 miles to return home 48 hours before another match is “setting him up for injury,” Olsen stated two weeks ago.

Since joining United in late June, De Rosario has contributed 11 goals and seven assists in 15 appearances. Despite the importance of the Vancouver match, United was obligated to release him because Canada’s qualifier falls at the end of a week-long international period set aside by FIFA, soccer’s global governing body.

MLS minimized the impact of player call-ups on its clubs by scheduling only three league matches (instead of the usual nine or more) during the window. But by arranging the United-Whitecaps game, as well as a Chicago-Dallas match Wednesday, the league ended up impairing all of those teams except Vancouver.

Guatemalan midfielder Marco Pappa is not expected to play for Chicago and U.S. midfielder Brek Shea, a league MVP candidate with Dallas, will probably sit out.

United is also missing central defender Dejan Jakovic, who isn’t quite ready to return from a hamstring injury that has sidelined him since late August. On the brighter side, Brandon McDonald is back from a yellow card suspension, fellow center back Ethan White (sprained knee) has been cleared to play and goalkeeper Bill Hamid was released from U.S. national team duty.

“It’s a big one,” Wolff said of the Vancouver match. “We know a win would put us in a nice position heading into the final three games, but it doesn’t just happen by itself. We’ve got to go out and get it.”